It is necessary in connection with the high-performance, fully automatic stacking of containers of various shapes and geometries, which can be automated, to construct stacking machines that are capable of stacking a great variety of kinds of containers. In terms of their systems, the stacking machines are so-called column stackers. The stacking of containers is part of an overall logistic solution for sorting containers that can be automated.
To increase performance and efficiency, containers are not moved through the plant as individual boxes but in stacks on feed sections. The maximum stack height is limited for every individual kind of container. The distribution of the containers on the feed sections is chaotic (random), i.e., the order and the stack height in which the individual kinds of containers arrive at the area of automatic stacking are not known or cannot be manipulated. A stacking machine is capable, in principle, of stacking a plurality of kinds of containers. A single kind of container is always associated with a column stacker during the running operation. Kinds of containers can be characterized by different areas, different container heights, and, e.g., different patterns and colors while the external geometry is the same.
The control of the entire plant guarantees that only the one kind of container is fed to the stacking machine. The stacking machine is a column stacker, which forms towers of a defined height depending on the kinds of containers.
The stacking machine grips for this purpose a stack of containers of a defined height and lifts it up. A subsequent stack of containers of, for example, another height moves into the machine. The machine places the lifted-up stack onto the introduced stack, repositions itself and grips both stacks and lifts up both. Another stack of, for example, yet another height is now moving in. The process is repeated until a tower of defined height has formed. It appears from the above description that only a single stack of containers can enter the stacking machine at any time, namely, when the stack is lifted up in the machine.
A prior-art stacking machine can stack large, but also small containers. It is disadvantageous that the performance capacity of the machine is not fully utilized when stacking smaller containers, because the machine is designed, by virtue of its dimension, for large containers with a large area.